You can use pre-built images even with plain LXC: lxc-create -t download -n container1 -- -d ubuntu -r trusty -a amd64 LXD just takes it a little further, so

You can use pre-built images even with plain LXC: lxc-create -t download -n container1 -- -d ubuntu -r trusty -a amd64 LXD just takes it a little further, so on the UI level you are dealing just with images through the whole life-span of the container, not just when you are creating it. That makes it possible to wrap it all in a nice API and automatize the environment.